The invention relates to a method for predicting the voltage of a battery, in particular of a vehicle battery.
One problem that traditionally occurs is that, for example in a motor vehicle power supply system, the voltage collapses in certain load conditions when the battery is poor or discharged to such an extent that important systems, such as the braking system, no longer operate fully and, in some circumstances, the driver can then operate the vehicle only with major restrictions.
DE 39 36 638 G1 discloses a method in which the loads on a vehicle power supply system are switched off or reduced when the vehicle battery state of charge falls below a specific level, in order to prevent excessive discharging of the battery. Which load or loads is or are switched off depends on the group of loads to which it or they belong. By way of example, one such group is composed of “conditionally switchable loads” (BSV) and/or “switchable loads” (SV). The group is in this case always completely switched off, or its consumption is reduced. Each group has a priority relating to vehicle safety and/or its importance. The process of switching off or reducing the individual groups starts with the group with the lowest priority. If this does not lead to an improvement in the state of charge of the battery, further groups are switched off or reduced successively until the battery state of charge reaches a specific level.
Furthermore, DE 199 60 079 A1 discloses a method for switching various classes of loads on and off by means of switching elements within an energy management process, which is carried out by a controller. The switching elements are in this case actuated such that the selected priorities for actuation of the switching elements can be changed dynamically during operation. The switching priorities can thus be adapted as a function of the operating state during operation. Loads are switched off by varying the switching priority such that the perceptibility of the operating states is as far as possible suppressed.
When using this conventional method, a load or a group of loads is switched off or reduced only once a poor state of charge has already been found. In order to prevent a safety-relevant system, such as the braking system, no longer being fully operationally available as a result of being reduced, a computation-intensive method is in this case currently used to calculate the state of charge of the battery, and this considerably increases the costs of the associated controller.
One object of the present invention is thus to provide a simple and cost-effective method for predicting the voltage of a battery, by means of which a state in which the battery is poor or discharged and in which a voltage drop can occur in certain load conditions can be predicted, and which has appropriate countermeasures to be initiated before this state occurs, in order that specific safety-relevant loads remain fully operational.